Three component zoom lens for photographic miniature cameras



35o-42? 5R SEARCH 200M f? OR 32709615 v 7,35 "TJ" Spt 6 T H A v FC? THREE comonoml L'LCSHSRHIEHOTOGRAPHIC3,270,615 Y MINIATURE CAMERAS 2 l 7 Filed July 1l. 1962 Fig l F i g 2 f Ll L2 La W A w A w A@ A y;

F g 5 F i g' 4 L1 Lz La 1 1 L2 La f| 0f2 0 fs 0 fl f2 f5 dLSLlL+H Il dvs+m I l m- 2 di -fl INVENTOR.

BY l

United States Patent O 3 270 615 THREE COMPONENT zooM LENS FOR PHOTO- GRAPHIC MINIATURE CAMERAS Takashi Higuchi, Hodogaya-ku, Yokohama-shi, Japan,

assignor to Nippon Kogaku, K.K., Tokyo, Japan, a corporation of Japan Filed July 11, 19,62, Ser. No. 209,024 Claims priority, application Japan, Aug. 15, 1961, 36/28,904 3 Claims. (Cl. 88-57) With prior art zoom lens designs of two components, one of which is negative and the other positive as illustrated in FIGURE l, an unbalance is likely to occur in the corrections for aberration resulting from changes in the focal length, especially over-correction for spherical aberration when long focal lengths are involved, because of the limited degree of freedom available in such designs for aberration correction.

The majority of the zoom lenses developed up to the present have been intended for use in motion-picture and television cameras, and it might be well observed that none of them could stand practical use in still cameras, which are subject to high performance demands as concerns their size and sharpness of image. And, specificially, in theory and in practice it is more difficult to produce zoom lenses, applicable also for photography of wide angular fields, for use in still cameras.

There are considered to be two plans for producing zoom lenses which should satisfy the demands for high performance:

(1) The `focal lengths and the principal plane distances of the zooming components should be proportionally magnified so that the optical burden on each of the components of the optical system might be alleviated; and

(2) Non-spherical surfaces should be utilized.

Reflecting on these plans gives rise to the view, that perhaps the resulting zoom lens is of poor portability due to the increase in size and weight of the optical system to be mounted in a still camera on the one hand, and that of the questionable mass production of non-spherical lenses on the other. Hence the conclusion that such plans do not give a proper clue to the solution of the problem we ar'e facing.

However, the present invention, without being made captive of either of such plans departs therefrom, and has made possible the development of a complete zoom lens system for use in still cameras, which system is not only of unique design, but also is of the least possible size and weight and has the best aberration correction attained. Furthermore, the invention has removed the above-mentioned defects and successfully developed a superior zoom lens system of remarkable aberration correction without incurring any increase in size.

A clear concept of the scope and purposes of this inveiltion will be obtained from the `following description taken with the drawing in which:

FIGURE l is a diagram illustrating the basic design of prior art zoom lenses comprising two components, a negative and a positive component in that order;

FIGURE 2 is a diagram illustrating the basic design of the present inventive lens comprising an immovable second negative, and mechanically movable first and third components;

FIGURE 3 is a diagram illustrating the normal position of the components of the inventive lens prior to movement of the movable components;

FIGURE 4 is a diagram illustrating the position of the components of the inventive lens, as the positive first and third components are moved by distances m and l, respectively, from their normal positions with the negative second component remaining positioned therebetween; and

ice

FIGURE 5 is an illustrative embodiment in accordance with the invention.

In accordance with the invention, the first negative component of the prior art zoom lens design comprising two components, one negative and the other positive, is divided into two components: positive component L1 and negative component L2, so that the complete lens system comprises three components: positive component L1, negative component L2 and positive component La.

In other words, the first component L1 is a convergent, the second component L2 a divergent, and the third component L3 a convergent, lens system; the positive first L1 and third L3 components being mechanically movable and the negative second component L2 remaining immovable therebetween, thereby producing continuous magnification and always defining the focal plane at a certain definite spatial position.

On the other hand, the movement as a unit of the third positive component L3 and the built-n aperture stop renders it possible to minimize the size of the over-all lens system and to stabilize corrections of the aberrations. The

use of a positive lens as the first component L1 expediently` works for the bundle of rays, rendered convergent thereby, to be received by the second L2 and its follower components to the complete solution of the over-correction problem, especially thatof spherical aberration, without incurring heavy size of the over-al1 system.

Now assume the 4focal lengths for the first positive L1 (movable), second negative L2 (immovable) and the third positive L3 (movable) components to be f1, f2 and f3, respectively, and the spacings between the principal planes of the components to be d1 and d2, respectively. Further assume that the spacings are dlg and dzs in the case of the particularvstandard con-dition at which the over-all focal length of the system is the shortest, and that these spacings become du, and du, when the third positive component L3 is moved distance l from its position in said standard condition. Then, when it is desired to determine the necessary distance m for the first positive component L1 to move in terms of distance l through which the third positive component L3 has moved from its standard position, so as to have the focal plane always at a certain definite spatial point during image magnification, the following formulae are obtained:

where bas denotes the distance between the image point and the third positive component L3, the image point being formed of the infinity object point by the rst positive L1, the second negative L2 and the third positive L3 components as they are positioned in said standard condition.

And the most effective combination of f1, f2 and f3 in connection with the optical performance of the lens, the zoom ratio, the functions of the movable components and other items, meets the following conditions:

0-2i lfalojfi 0-9|f2|f3 llfal (4) A practical example of zoom lens design in accordance with the invention will now be described in connection with the illustrative embodiment thereof of FIGURE 5 obtainable on the basis of the functions of the movable components, under a number of limitations set from the viewpoint of aberration correction, which include:

I. The rst positive component Li is moved in unison with the third positive component L3, and, in order to correct for unbalanced astigmatism and the negative distortion in the wide angular field as well as to improve where r1, r2 rm denote the radii of the curvature of respective component elements;

di, d2 dia, the thicknesses of the respective component elements and of the air spacings therebetween, I

the sine condition, the most forwardly surface of the both on the optical axis; rst positive component L1 has a radius of curvature r1 n1, n2 nq, the indices of refraction of the respecwithin the limits: tive glass materials measured for the D-line of spectrum;

and 0.5flri Llfi (5) v1, v2 v7, the Abbe numbers for said glass materials. II. The second negative component L2 is made the Y AS has been Stated, .the production of a zoom lens immovable component and divided into a plurality of two for 5ml camcfa fulfilling the dcmal'd fOr Very Sharp 0r three elements (two are shown in FIGURE 5) to preimage formation is rather difiicult practically and theoretivent over-correction for spherical aberration when long cally, S0 long aS the prior artdesign is accepted as the focal lengths are involved; and, to remove distortion aberl5 gulde- II! QOIlraSt, the adoption of the. design of the ration when a wide angular field is involved, the first surlens Systcm m accordance Wlth thc Invention cn'aclcs thc face of the most forwardly element of the divided Compoconstruction of zoom lenses extremely small 1n size and nent L2 has the selected radius of curvature r3 and the bcstccl'fcctcd fcfabcffat101- gewild surface of ,4, lying within the iimiis: Furthermore, the production of cameras with the cornpact built-in zoom lens provided by the invention spares the user thereof the trouble of mounting ancillary or 4 4 1-2N|f2llf3| (o) interchangeable lenses, and provides means to control 0.4Nif2lr4l-5Nlf2] (7) a covering power, ranging from the wide angular field to that of telephotography, with the use of but a single HL The third positive component L3 is moved in com 25 lens, improving to a remarkable extent proper maneuvernection with the first positive component L1 and, to have ablhty of sul! cmeras' it function as the image forming component, is provided what I clam 1S: with Ia built-in aperture stop. This component consists 1' A 2.00m leccompnsmg three components of which of two or three positive elements (two being Shown in the first is a positive movable component of focal length FIGURE 5) one negative element and, rearmost, one 30 f5 thc Second 1S afl mmovablc negatlfc componcnt con positive element, the negative element satisfying the fo'lslstmg of 'a Plurahty N up to three blconcave alrSPaced lowing conditions': negative lens elements, the second component having a focal length of f2, and the third is a positive movable y component of focal length f3, and consisting of two posi- Ogfalrllllgfi (8) 35 tive lens elements, a negative lens element and a positive 0.5/3r121-3f3 (9) lens element air spaced in that order, the second component is spatially fixe-d between the first and third where r11 and :'12 denote the radii of curvature of the mochancauy movable oomponents the lens array sans' first and second surfaces of the negative element, respecfymg the following Condmons' tively. These conditions Work to effectively remove un- 0-5f1S r1 $1.1 f, balances in aberration or changes in focal length produced O'gfl S f2 Sojfl by the first positive L1 yand the second negative L2 com- 9 ponents; above all, Condition 8 is effective for correcting o' lftl f3 -18lf2l for spherical aberration and curvature of image field, 1.2Nfz r3 Sw and Condition 9 for improving the sine condition and 0.4Nif2l r4 S 1.5N I f2l removing coma and astigmatism, contributing thereby to 0 9 l 1 g the successful design of zoom lenses of small size and fs- T111- "f3 best aberration correction. 0.5f3S T12 l.3f3 The inventive zoom lens contemplates the use thereof l: 612s.. 2L in still cameras,` but it is also capable of use in motionv f2(d2s ,l)(b3s+l f3) f2f3(b3s+l) picture and television cameras. m=fid1s i d b l b b Data of an illustrative embodiment of the invention zS-ZX ss-l' *fil-fs( ssil)f2( :isll-f3 are given below: where rsubscripi is the radius of curvature of the succes- EXAMPLE U=1o0tois81 Ti er t lt. nml-169.917

,lmnltrS/ifgepo' {TP 428'034 1i-12.82 rit-1.61948 ti-sas d=7.13 to 36.24 r3=18a759 d3=i.91 m=1.610o5 v,=47.0 The second negative comrz'l'mosx d :8 75 ponent f2=-60.45 (L1). 1 5: 120'781 d5=i.91 n;=1.67005 v,=47.0 fwd-515.788

d=42.25 to 10.11 r1=+196-s77 d1=7.94 ni=1.69227 vi=53.3 r=-i23.387

da =0. 32 r =+61.i30 i +976 117 du =8.`26 7L5=1.69227 1J5=53.3 The third positive compo- "D: f

nent fa=A5 (La). r1]: 119'362 d"13")0 l d11=17.79 n=1.73954 u=27.7 m=+66.393

dn=6.35 rlp-1441.990

dn=ii.i2 m=1.70063 v1=40.7 T14=75.107

sive surfaces of the lens elements, the subscripts increasing in the order of location of the respective surface from the object to the image side of the zoom array, m is the distance through which the first component is movable, l is the distance through which the third component is movable, dlg the air spacing between the printhird components when each is at its position for the minimum overall focal length of the zoom lens array. 2. The zoom lens according to claim 1 in which N, the number of lenses in the second component, is two.

3. The zoom lens according to claim 2 having the following detailed data:

[Overall focal length-minimum 100; maximum 188] First compenent f 197 .97

Second component f2:

Third component f= cipal planes of the iirst and second components, das the air spacing between the principal planes of the second and third components, both :11S and dzs being taken at the component positions at which the overall focal length of the zoom array' is the shortest, du, and du, the air spacings between such principal planes when the third component has moved the distance l and the rst component the distance m, and bas is the distance between the third component and the image point formed where rsubsmpt denotes the radius of curvature of the respective lens element surface, dsubscripb the thickness of the respective lens element and the respective air space, nsubsmpt the index of refraction for the D-line of the spectrum of the optical material of the respective lens element, and vsubscript the Abbe y number thereof, the respective subscripts of each of r, d, n, and v increasing in the order of their location from the object to by the object point at infinity by the rst, second and 40 the image side of the lens array.

References Cited by the Examiner UNITED STATES PATENTS 2,847,907 8/ 1958 Angenieux 88-57 3,023,673 3/1962 COX et al 88--57 3,127,466 3/1964 Walters 88-57 OTHER REFERENCES Wright: Boom in Zoom for 35mm., Photography, vol. 50, No.5, May 1962, pp. 56-61.

DAVID H. RUBIN, Primary Examiner. JEWELL H. PEDERSEN, Examiner.

JOHN K. CORBIN, Assistant Examiner. 

0.5F1< R1 <1.1F1 0.2F1< F2 <0.5F1 0.9 F2 < F3 <1.8 F2 1.2NF2< R3 <$ 0.4N F2 < R4 <1.5N F2 0.9F3< R11 <1.8F3 0.5F3<R12 <1.3F3 L=D2S-D2L F2(D2S-L) (B3S+L-F3) -F2F3(B3S+L) M=F1-D1S+ (DS2-L)(B3S+L-F3)-F3(B3S+L)-F2(B3S+L-F3
 1. A ZOOM LENS COMPRISING THREE COMPONENTS OF WHICH THE FIRST IS A POSITIVE MOVABLE COMPONENT OF FOCAL LENGTH F1, THE SECOND IS AN IMMOVABLE NEGATIVE COMPONENT CONSISTING OF A PLURALITY N UP TO THREE BICONCAVE AIRSPACED NEGATIVE LENS ELEMENTS, THE SECOND COMPONENT HAVING A FOCAL LENGTH OF F2, AND THE THIRD IS A POSITIVE MOVABLE COMPONENT OF FOCAL LENGTH F3, AND CONSISTINGOF TWO POSITIVE LENS ELEMENTS, A NEGATIVE LENS ELEMENT AND A POSITIVE LENS ELEMENT AIR SPACED IN THAT ORDER, THE SECOND COMPONENT IS SPATIALLY FIXED BETWEEN THE FIRST AND THIRD MECHANICALLY MOVABLE COMPONENTS, THE LENS ARRAY SATISFYING THE FOLLOWING CONDITIONS: 